class Counter{
    private int count=0;
    private Object locker=new Object();
//    synchronized public void add(){
//        count++;
//    }
    public void add(){
        synchronized (locker) {
            count++;
        }
    }
    public int get(){
        return count;
    }
}
public class demo02 {
    public static void main(String[] args) throws InterruptedException {
        Counter counter=new Counter();

        Thread t1=new Thread(()->{
            for (int i = 0; i < 10000; i++) {
                counter.add();
            }
        });
        Thread t2=new Thread(()->{
            for (int i = 0; i < 10000; i++) {
                counter.add();
            }
        });
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println(counter.get());
    }
}
